In general, a canister of the kind mentioned above has an adsorption chamber communicating with a passage communicating with atmosphere (hereinlater, called atmosphere communication passage) and a filter element in shape of sheet formed from felt or like is arranged at an end portion of this adsorption chamber. This filter element captures powdered coals generated, from activated carbons or charcoals filling in the adsorption chamber, through the mutual rubbing thereof caused by vibration or oscillation of a vehicle, and the filter element prevents the captured powdered coals from being discharged outside a canister case through the atmosphere communication passage.
Furthermore, prior art also provides a canister which is provided with a dust removing filter element of a type different from that of the canister mentioned above for the purpose of removing dust or like in the atmosphere taken into the canister through an atmosphere communication passage at a time of purge.
For example, Japanese Patent Laid-open (KOKAI) Publication No. HEI 11-280569 discloses a canister including an adsorbent case in which a filter chamber is formed independent from an adsorption chamber, and in the filter chamber, a filter element for filtering air taken into the filter chamber through an atmosphere communication passage is disposed. This filter chamber is arranged by being fused to one surface of the canister or being connected independently from the canister.
In the canister disclosed in the publication mentioned above, however, a canister body has an increased lateral width, making large an entire structure or shape thereof, which influences canister location space in a vehicle, thus providing an inconvenience. Furthermore, in the arrangement in which the filter chamber is independently disposed, the number of parts or members increases, and a manufacturing cost is also increased because of the fusing process or like, also providing a disadvantage. Still furthermore, there may provide a problem such that the filter element is clogged by dust or like absorbed through the atmosphere communication passage, which may result in shortage of lifecycle of the canister.
In view of the defects or drawbacks encountered in the prior art mentioned above, the present invention aims to provide a canister having a structure capable of removing dust or like and preventing clogging of a filter element without changing basic design or shape of the canister.